Avoid copying undo data

src/main.cpp

@@ -1351,12 +1351,13 @@ void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCach
     bool ret;
     // mark inputs spent
     if (!tx.IsCoinBase()) {
-        BOOST_FOREACH(const CTxIn &txin, tx.vin) {
+        txundo.vprevout.reserve(tx.vin.size());
+        for (unsigned int i = 0; i < tx.vin.size(); i++) {
+            const CTxIn &txin = tx.vin[i];
             CCoins &coins = inputs.GetCoins(txin.prevout.hash);
-            CTxInUndo undo;
-            ret = coins.Spend(txin.prevout, undo);
+            txundo.vprevout.push_back(CTxInUndo());
+            ret = coins.Spend(txin.prevout, txundo.vprevout.back());
             assert(ret);
-            txundo.vprevout.push_back(undo);
         }
     }
 
@@ -1663,6 +1664,7 @@ bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, C
     CDiskTxPos pos(pindex->GetBlockPos(), GetSizeOfCompactSize(block.vtx.size()));
     std::vector<std::pair<uint256, CDiskTxPos> > vPos;
     vPos.reserve(block.vtx.size());
+    blockundo.vtxundo.reserve(block.vtx.size() - 1);
     for (unsigned int i = 0; i < block.vtx.size(); i++)
     {
         const CTransaction &tx = block.vtx[i];
@@ -1698,10 +1700,11 @@ bool ConnectBlock(CBlock& block, CValidationState& state, CBlockIndex* pindex, C
             control.Add(vChecks);
         }
 
-        CTxUndo txundo;
-        UpdateCoins(tx, state, view, txundo, pindex->nHeight);
-        if (!tx.IsCoinBase())
-            blockundo.vtxundo.push_back(txundo);
+        CTxUndo undoDummy;
+        if (i > 0) {
+            blockundo.vtxundo.push_back(CTxUndo());
+        }
+        UpdateCoins(tx, state, view, i == 0 ? undoDummy : blockundo.vtxundo.back(), pindex->nHeight);
 
         vPos.push_back(std::make_pair(tx.GetHash(), pos));
         pos.nTxOffset += ::GetSerializeSize(tx, SER_DISK, CLIENT_VERSION);